The decentralized advocacy group says it disavows violence while spreading a belief that “badges don’t grant extra rights.”

But the Millers, described by investigators as anti-government extremists, had a deadly animosity for authority.

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Officer Alyn Beck was remembered as a loyal husband and dedicated father to his three children. (AP)

“Bout time to start killing cops, eh?” Miller, 31, wrote in May when he shared a viral video of police brutality on Facebook. “Maybe if we can kill all these despotic goons they will turn on their masters and once again be public servants and we can end this madness.”

After a historic decline in the number of police officers fatally shot last year, 2014 has rebounded to previous levels. Beck and Soldo are among 28 U.S. officers shot and killed in the line of duty so far this year. The most recent death came Sunday, when rookie Jersey City, N.J., Officer Melvin Santiago was ambushed by a gunman who reportedly told people he was “going to be famous” for killing a cop.

Such shameless bravado — online and off — and an exploding right-wing movement are creating anxiety about attacks against police.

“There's a deep concern that there has been a measurable increase in violence against police officers, especially with firearms,” said Rich Roberts, spokesman for the International Union of Police Associations. The anti-police movement “seems to feed off each other online,” he said.

The FBI has increased warnings about possible threats to law enforcement, multiple police sources told Yahoo News. The bureau declined to confirm any change.

This follows a 2009 Department of Homeland Security report that included a warning about domestic extremists using the Internet to recruit members, share tactics and raise hate to an all-time high.

Rich Stanek, who chairs the National Sheriffs’ Association Homeland Security Committee, said he proudly protects constitutional rights, but he worries social networking gives radicals such as Miller a false sense of recognition.

“They can post, blog and do so freely and anonymously without any accountability whatsoever,” said Stanek, sheriff of Hennepin County in Minnesota.

Escalating danger by anti-government extremists dominated a four-hour discussion on homeland security at last month’s National Sheriffs’ Association conference, said Stanek, who commands an 800-member department in Minneapolis.

Trent Nice, a former neighbor of Miller’s in Lafayette, Indiana, frequented his friend’s Facebook page.

“I shared a lot of his views, but would never do anything like that,” Nice told Yahoo News by email.

The week of the June 8 rampage, Nice gave an approving click to Miller’s Facebook manifesto predicting pending bloodshed and war.

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Officer Igor Soldo and his wife, Andrea, would have celebrated their son&#039;s first birthday on July 7. (AP)

“As far as me liking the post, if that’s what he intended when he posted it, then I severely misunderstood his post,” he wrote. “His heart was in the right place. His head wasn't.”

Meanwhile police near Lafayette, where the Millers lived before moving to Las Vegas, are reportedly keeping an eye on the 765 movement, a new anti-police group on Facebook.

Sam Bradbury, a group member, was jailed in late June for posting a detailed Facebook messagethreatening to kill multiple authorities and destroy a courthouse “in a blaze of glory.” Arresting officers also recovered six bags of bomb-making material from the 22-year-old’s home.

Bradbury is being held on federal charges of using electronic communications to threaten injury to a person and destroy property with an incendiary device. According to an FBI affidavit, Bradbury ended his Facebook rant by writing “FREE SPEECH EXERCISE FOOLS” in parentheses. But a judge ruled he did not have to accept Bradbury’s First Amendment disclaimer and ordered him held without bail until an arraignment later this month.

The Bradbury arrest is similar to a spate of recent prosecutions “for alleged threats conveyed on new media, including Facebook, YouTube, and Twitter,”according to a brief filed in a pending Supreme Court case. Free speech advocates want the court to clarify what constitutes a true threat in today’s digital world.

Mark Potok, an expert on extremism, said he believes it is rare for social media to inspire someone to kill.

“However, the kinds of people who are prone to those kinds of hatreds find validation and real community on the Internet,” said Potok, a senior researcher with the Southern Poverty Law Center.

Last week the SPLC issued a report warning law enforcement about the increasingly hostile anti-government movement, which it estimates has grown from 150 groups in 2008 to nearly 1,100 last year.

The economic crisis, proposed gun control, Barack Obama’s election, NSA spying and the militarization of police among other issues have spurred the resurgence, the watchdog organization said.

“There’s a hell of a lot of anger out there in certain corridors,” Potok told Yahoo News. “Jerad Miller was not the only one who saw police in the United States as Nazis.”

Miller found an approving audience for his conspiracy theories and political tirades online. Some Facebook posts were original, but he shared others from pages he frequented such as Patriot Nation, Taxation is Theft and Cop Block.

“There was blanket rejoicing over the deaths of two people and I don’t think that’s good in any situation,” Eyre said. “It didn’t fit Cop Block ideology. The site’s not an anti-police thing; it’s like a pro-personal empowerment site.”

Launched in 2010, Cop Block encourages the public to submit home videos, photos and stories of rogue officers for discussion.

Eyre said the Vegas entry was put up by a former volunteer who still had administrative access. The post and its removal provoked days of intense debate on the Cop Block Facebook page, which included the following comments:

“You don't promote accountability; you promote anti-police, anti-government behavior by publicizing criminals and making them out to be heroes.”

“A cop died, opinions were stated... don't think a cop wouldn't be bragging about shooting you over some drinks with his cops buddies while he enjoys his 2 weeks paid vacation...”

By its own account, the 2011 blog post “WHEN SHOULD YOU SHOOT A COP” is one of Cop Block’s most read. A week before the Vegas slayings, a photo on Cop Block’s Facebook page portrayed a dead officer with the words: “This is what a good cop looks like.”

Melissa, who requested that her full name not be used for safety reasons, said she and other police spouses are frustrated by Facebook’s lack of action in response to their Cop Block complaints.

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A post from Jerad Miller's Facebook page four weeks before his deadly rampage. (Screenshot)

A Facebook spokesperson told Yahoo News in a statement: “People come to Facebook to share experiences of the world around them and on occasion this may result in the sharing of content that some may find upsetting. We encourage anyone who sees content that violates our community standards to report it to us.”

Photos promoting officer deaths posted as comments to Cop Block’s page on May 25 and June 1 were removed by Facebook after being contacted for this story.

“I understand the need for people to express their opinion, but I think there is a line that has to be watched,” Melissa said. “When does an opinion become a plan of action?”

Nice hadn’t seen Miller in a few years, but his Facebook connection earned him a visit from FBI agents after the Las Vegas murders.

“I told them if they wanted to investigate someone, go investigate Barack Obama,” he recalled. “They kinda just had a smirk on their faces when I said that, and said well we're investigating this right now. I don't know if (they) were trying to get background on him or find out if there are more crazies like him.”